UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF PREVENTION, PESTICIDES 

AND TOXIC SUBSTANCES

Probabilistic Analysis

Probabilistic Analysis for the Notice of Intent to Cancel Noncompliant Rodenticide 

Products Containing Brodifacoum, Difethialone, Chlorophacinone, Diphacinone, 

Warfarin, or Bromethalin

January 24, 2013 

Office of Pesticides Programs 

Prepared by: 

Elizabeth Riley

Office of Pesticide Programs
While the relative sensitivity of the standard test species used in the deterministic assessment is 

unknown, EPA conducted a probabilistic analysis that varied whole body residue and acute 

toxicity values to inform the level of confidence and explore uncertainty in the likelihood that a 

randomly selected secondary consumer may achieve a lethal rodenticide dose. This was 

accomplished using a Monte Carlo simulation with a distribution of possible outcomes that were 

analyzed to allow for more thorough understanding of the uncertainties associated with the 

available data. The modeling exercise was performed by varying selected parameters for liver or 

blood-plasma half-life and the LD50 or LC50. The metric for comparing chemicals was based on 

probability density functions for percentage of species with Risk Quotients (RQs) above the 

acute Level of Concern (LOC) value of 0.5 (USEPA, 2004). This represents the likelihood that 

an animal feeding on prey containing rodenticide could receive a dose that exceeds 1⁄2 the LD50 

for a secondary consumer with the expectation that the greater proportion of outcomes resulting 

in an LOC exceedance, the greater the potential for adverse outcomes. 

1.1.1. Methods

EPA employed a Monte Carlo-based approach in order to evaluate uncertainty regarding toxicity 

values for an animal encountering prey that has ingested a rodenticide. The approach also 

evaluated uncertainty related to the accumulation potential of each rodenticide in prey species. 

In this approach, distributions were developed for the exposure (i.e., liver or blood plasma halflife) and effects variables (i.e., LD50 or LC50 values) to derive a distribution of RQs. This was 

accomplished using CrystalBall (version 7.3.1). This distribution was then used to determine the

probability that an RQ value would be above the LOC (RQ is at or above 1⁄2 the LD50) for 

secondary consumers (e.g., predator and scavenger birds). EPA compared the rodenticide results 

in this “probability to exceed” model with the expectation that the greater proportion of random 

outcomes resulting in a risk exceeding EPA’s level of concern, the greater the potential for 

adverse outcomes. 

Because the objective of the analysis was to investigate the influence of accumulation potential 

and toxicity on the comparative interpretation of risks among the rodenticides, EPA treated all 

model inputs that were not specific to any rodenticide as fixed values. For purposes of 

comparing rodenticide active ingredients, the major assumptions for fixed variables in the model 

were:

• Body weights assessed for birds at risk through secondary exposure were 100g, 1000g, 

and 5000g. 

• 100% of secondary consumer’s diet is intoxicated primary consumers.

• 100% of primary consumer’s diet is dry, rodenticide bait. 

• Rodenticide intake in the secondary consumer was calculated based on allometric 

equations found in the Wildlife Factors Handbook (USEPA 1993).

• For the anticoagulant rodenticides, 1-day, 6-day, and 14-day accumulation periods based 

on consecutive feeding events in primary consumers were selected to represent the range 

of accumulations possible from one anticoagulant rodenticide placement. For 

bromethalin, the analysis focused on a 1-day accumulation period because bromethalin’s 

rapid mode of action limits the accumulation potential of the chemical. A recent study by 

Pitt et al. (2011) found that time to death for house mice, Polynesian rats (Rattus exulans) 

and black rats (Rattus rattus) offered bromethalin may occur within 1-3 days. Data from 

this study also indicates that house mice and Polynesian rats exposed to bromethalin stop 
feeding on the bait after reaching a lethal dose, further reducing the potential for 

accumulation. These data suggest an analysis that uses 1-day accumulation in the prey is 

unlikely to underestimate accumulation of for bromethalin.

• The body weights for house mouse (23g) and Norway rat (485g) were used to represent 

the body weights of primary consumers likely to feed on the rodenticide bait.

• Concentration of rodenticide in bait was based on the labeled concentration.

The parameters allowed to vary in the model were:

• Acute toxicity endpoint of secondary consumer (i.e., LD50 and LC50 values); 

• Half-life of rodenticide in prey (as measured in liver for anticoagulants or blood-plasma 

for bromethalin).

Acute toxicity data for each of the rodenticides are described in Appendix A of the SAP 

Background Document. The availability of species-specific acute toxicity data varies among the 

rodenticides, with warfarin having the largest dataset (9 data points) and difethialone the smallest 

(4 data points). Similarly, the availability of acceptable half-life data varies widely among the 

rodenticides. Brodifacoum, with 12 liver half-life values and 8 blood-plasma half-life values, 

represents the greatest data availability, while chlorophacinone and bromethalin only have one 

half-life value available each (measured in liver and blood-plasma, respectively). 

Because the toxicity data for each chemical may have come from different test species, LD50 

values were normalized for body weight to a 1kg animal using EPA’s standard method of 

calculating weight-adjusted toxicity values. These normalized LD50 values were then adjusted to 

standard body weights representative of secondary consumers of interest (100g to 5,000g for 

birds) in the equations used to calculate RQs. After all of the data were compiled, the range of 

individual data points for toxicity and metabolic half-lives for each rodenticide were each 

represented as a probability distribution, fitted to log normal distributions. The result was 5 

different distributions of chemical-specific parameters for each rodenticide (2 different 

distributions for the 2 toxicity endpoints and 1 for the metabolism half-life), except in cases 

where there were less than two data points for a particular parameter, such that probability 

distributions could not be created. For example, there is only 1 LC50 value available for 

diphacinone, while chlorophacinone and bromethalin each have only 1 half-life value (for liver 

and blood plasma, respectively). In those cases the single available toxicity or half-life value 

acted as a fixed variable in the model. Toxicity distributions were truncated at the 2.5th and 97.5th

percentiles to reduce the potential for unreasonable extreme values in the data sets and to 

maintain a range of toxicity more reflective of the available data. Similarly, half-life values were 

truncated at the lowest and highest values observed in the open literature and registrantsubmitted studies. Once the data were fitted to log normal distributions, a random value was 

generated using the parameters of the fitted distribution using the forecast function within the 

CrystalBall program. The randomly selected value was then used in the equations to calculate an 

RQ value. The Monte Carlo simulation repeated this process 10,000 times to create a distribution 

of RQs for each of the scenarios of interest. 

1.1.2. Results

Although EPA performed the probabilistic assessment for predator/scavenger birds and 

mammals, the results and conclusions sections of this response will focus on birds at risk through 
secondary exposure, which are the subject of the SAP comment. The probabilistic assessment for 

mammals at risk through secondary exposure sheds no new light on the issues in the proposed 

cancellations, as it simply confirms, as did the Agency’s deterministic assessment, that 

rodenticides designed to target mammalian species will be toxic to mammals regardless of 

whether they are primary or secondary consumers. However, the enhanced toxicity and extended 

residence time in non-target animals suggests that bioaccumulation potential and resulting 

secondary poisoning potential of brodifacoum and difethialone are greater relative to the other 

assessed rodenticides. The results of the probabilistic assessment for birds are shown in tables 

below (Tables 1-4). The percentage values, which represent the likelihood a randomly selected 

bird from a particular weight class may acquire a lethal dose under the assumption in this 

evaluation, were visually estimated from the graphical distribution of the various distributions. 

As an example, Figure 1 shows the distribution of RQs for large raptors consuming small 

mammals exposed to rodenticide bait for 1 day (graphs for all exposure scenarios can be found in 

Appendix 1). The RQ value, in log scale, is displayed along the horizontal axis and the 

likelihood of a predator or scavenger of the particular class experiencing a lethal dose, expressed 

as percentages by increasing value, is displayed along the vertical axis. The vertical red line 

represents where the RQ value is equal to the LOC of 0.5. Portions of distributions that appear to 

the right of the vertical red line indicate species on the distribution with RQ values greater than 

the LOC, and thus at risk for mortality. The percentage of RQ values above the LOC are visually 

represented as the point where the distribution crosses the vertical red line, to the nearest 5%, 

subtracted from 100%. These percentages allow for the comparison of risks among chemicals 

where larger percentage values suggest a higher likelihood that a randomly selected bird may 

achieve a lethal dose under the assumptions of this analysis.
Figure 1. Distribution of Acute RQs for 5000g Birds Consuming Mice Exposed to Bait for 1 

Day

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Bromethalin

Chlorophacinone

Diphacinone
Acute Dose-Based Assessment

Ten thousand RQs were calculated for 100-g birds consuming mice or rats that are primary 

consumers of rodenticides based on the 10,000 randomly sampled LD50 and half-life values. For 

each rodenticide, the values in Table 1 provide the percentage of calculated RQs that were above 

the LOC for 100-g birds when toxicity and exposure parameters were randomly sampled. These 

percentages allow for the comparison of risks among chemicals where larger percentage values 

suggest a higher likelihood that a randomly selected bird may achieve a lethal dose under the 

assumptions of this analysis. Based on this analysis, birds have a high likelihood of receiving a 

dose that exceeds 1⁄2 the LD50 (RQ exceeds the LOC) when consuming prey species intoxicated 

with brodifacoum, difethialone and bromethalin, even where the prey have only consumed the 

equivalent of one day’s feeding. However, the likelihood of bird RQs exceeding the LOC from 

secondary exposure to difethialone is less than the likelihood resulting from secondary exposure 

to brodifacoum or bromethalin, even under the 1-day accumulation scenario. Relative to the 

risks of brodifacoum, difethialone and bromethalin, there is a lower likelihood that birds 

consuming prey contaminated with warfarin would receive a dose sufficient to result in LOC 

exceedances in all scenarios. Chlorophacinone and diphacinone have still lower likelihoods of 

exceeding the level of concern, relative to the other assessed rodenticides, though it should be 

noted that sensitive 100-g birds feeding on small mammals exposed to diphacinone bait for 

extended period of time may exceed concern levels.

Table 1. Percentage of Acute Dose-Based RQs for 100 g Birds that are Greater than the 

LOC.

Duration of 

accumulation in 

prey (days)

Brodifacoum Difethialone Warfarin Chlorophacinone Diphacinone Bromethalin

House Mouse as prey

1 99% 60% 5% ~0% ~0% 95%

6 100% 80% 50% ~0% ~0% NA

14 100% 85% 75% ~0% 1% NA

Norway Rat as prey

1 70% 40% ~0% ~0% ~0% 10%

6 100% 65% 10% ~0% ~0% NA

14 100% 75% 30% ~0% ~0% NA

NA- not applicable. Animals consuming bromethalin are not expected to continue feeding on bromethalin bait for 

six or fourteen days. 

For each rodenticide, the values in Table 2 provide the percentage of calculated RQs that 

exceeded the LOC for 1000-g birds when toxicity and exposure parameters were randomly 

sampled. Based on this analysis, 1000g birds have a high likelihood of receiving a dose 

sufficient to exceed the LOC when consuming prey species intoxicated with brodifacoum and 

difethialone. However, there is a higher likelihood of risk from exposure to prey contaminated 

with brodifacoum than difethialone. For warfarin there is little chance of predator/scavenger 

birds receiving a dose that may exceed the LOC, except under high accumulation scenarios. 

Bromethalin, chlorophacinone and diphacinone have lower likelihoods of triggering concern 

relative to the other rodenticides evaluated.
Table 2. Percentage of Acute Dose-Based RQs for 1000 g Birds that are Greater than the 

LOC.

Exposure Type Brodifacoum Difethialone Warfarin Chlorophacinone Diphacinone Bromethalin

House Mouse as prey

1 95% 40% ~0% ~0% ~0% 10%

6 100% 65% 15% ~0% ~0% NA

14 100% 75% 40% ~0% ~0% NA

Norway Rat as prey

1 60% 25% ~0% ~0% ~0% ~0%

6 100% 50% ~0% ~0% ~0% NA

14 100% 60% 40% ~0% ~0% NA

NA- not applicable. Animals consuming bromethalin are not expected to continue feeding on bromethalin bait for 

six or fourteen days.

For each rodenticide, the values in Table 3 provide the percentage of calculated RQs that 

exceeded the LOC for 5000-g birds when toxicity and exposure parameters were randomly 

sampled. Based on this analysis, 5000g birds have a high likelihood of receiving a dose 

sufficient to exceed the LOC when consuming prey species intoxicated with brodifacoum and 

difethialone. However, there is a higher likelihood of risk from secondary exposure to 

brodifacoum than difethialone. For warfarin, there is little chance of predator/scavenger birds 

receiving a dose that results in an LOC exceedance, except under high accumulation scenarios. 

Bromethalin, chlorophacinone and diphacinone have a lower likelihood of exceeding the LOC 

relative to the other rodenticides evaluated.

Table 3. Percentage of Acute Dose-Based RQs for 5000 g Birds that are Greater than the 

LOC.

Exposure Type Brodifacoum Difethialone Warfarin Chlorophacinone Diphacinone Bromethalin

House Mouse as prey

1 95% 30% ~0% ~0% ~0% ~0%

6 100% 55% 5% ~0% ~0% NA

14 100% 65% 15% ~0% ~0% NA

Norway Rat as prey

1 50% 15% ~0% ~0% ~0% ~0%

6 99% 35% ~0% ~0% ~0% NA

14 100% 50% ~0% ~0% ~0% NA

NA- not applicable. Animals consuming bromethalin are not expected to continue feeding on bromethalin bait for 

six or fourteen days.

Acute Dietary-Based Assessment

For each rodenticide, the values in Table 4 provide the percentage of calculated dietary-based 

RQs that exceeded the LOC for birds when toxicity and exposure parameters were randomly 

sampled. Based on this analysis, birds have a high likelihood of receiving a dose sufficient to 

exceed the LOC when consuming prey species intoxicated with brodifacoum and difethialone on 

a dietary basis. For warfarin and chlorophacinone there is little chance of predator/scavenger 

birds receiving a dose sufficient to exceed the LOC, except under high accumulation scenarios. 

Again, birds feeding on diphacinone and bromethalin contaminated animals have lower 

likelihood of exceeding concern levels relative to the other rodenticides evaluated.
Table 4. Percentage of Acute Dietary-Based RQs for Birds that are Greater than the LOC.

Exposure Type Brodifacoum Difethialone Warfarin Chlorophacinone Diphacinone Bromethalin

House Mouse as prey

1 100% 100% ~0% ~0% ~0% ~0%

6 100% 100% 1% 15% ~0% NA

14 100% 100% 15% 60% ~0% NA

Norway Rat as prey

1 95% 50% ~0% 0% ~0% ~0%

6 100% 100% ~0% 0% ~0% NA

14 100% 100% ~0% 5% ~0% NA

NA- not applicable. Animals consuming bromethalin are not expected to continue feeding on bromethalin bait for 

six or fourteen days.

1.1.3. Conclusions

For each chemical, results from the probabilistic assessment support the overall conclusions the 

EPA has drawn from the other lines of evidence (i.e., RQ estimates, quantity of contaminated 

mice or rats in diet required to consume the equivalent of an LD50, and results of the secondary 

feeding studies). Results of the probabilistic assessment indicate:

• Brodifacoum and difethialone pose greater secondary exposure risk to birds relative to 

the other chemicals assessed regardless of exposure scenario. 

• Bromethalin may pose secondary exposure risk to certain sensitive species (i.e., small 

birds consuming small prey animals); however, potential for secondary risk is somewhat 

limited due to the lower likelihood of continuous feeding of prey after reaching a lethal 

threshold and rapid mortality observed in primary feeding studies with bromethalin. 

Risks to small birds consuming large prey animals and risks to medium and large birds 

consuming small or large prey animals are substantially lower than for brodifacoum and 

difethialone.

• Warfarin may pose risk to certain sensitive species, especially under high accumulation 

scenarios; however, the likelihood of secondary exposure to exceed the LOC for warfarin 

is substantially lower than for brodifacoum and difethialone. 

• Diphacinone does not have a high likelihood of triggering secondary risk concerns 

regardless of accumulation scenario assessed. However, results of the probabilistic 

analysis indicate that there is a possibility that the most sensitive smaller secondary avian 

consumers modeled may be at risk from diphacinone poisoning under the highest 

accumulation scenario. EPA recognized potential for risks to this class of birds in the 

SAP background document. Secondary exposure risks for diphacinone are substantially 

lower than for brodifacoum and difethialone.

• For chlorophacinone, results of the probabilistic analysis for the acute dose-based 

exposure scenarios demonstrate a low likelihood of secondary exposure risk. However, 

results of the probabilistic assessment conducted for dietary-based exposure indicate that 

chlorophacinone may have a greater likelihood of posing risk to predator/scavenger birds 

under the higher accumulation scenarios than the one-day accumulation scenario. While 

these results represent a departure from the other analyses, the likelihood of secondary 

exposure risk for chlorophacinone is still substantially lower than for brodifacoum and 

difethialone. 
1.1.4. Uncertainties

Uncertainties associated with the available data are discussed in the SAP Background Document. 

Uncertainties associated with this type of probabilistic assessment have been discussed in 

previous SAP meetings (USEPA, 2001). A few of the important limitations are discussed below.

As discussed above, the availability of acute toxicity data varies widely among the rodenticides. 

Distributions created from few data points can result in significantly different estimates of risk 

depending on where the individual species lies on the sensitivity distribution, particularly at the 

extremes, i.e., opposite tails. Given that the avian toxicity datasets for each of the chemicals are 

relatively small (2 to 4 LD50 definitive values and 1 to 5 definitive LC50 values), EPA believes 

that this uncertainty is common across the chemicals and exerts a similar influence on the 

confidence of each chemical’s separate analysis. The availability of acceptable half-life data also 

varies widely among the rodenticides. Brodifacoum, with 12 liver half-life values and 8 bloodplasma half-life values, has the most data available, while chlorophacinone and bromethalin only 

have one half-life value available each (measured in liver and blood-plasma, respectively). As 

discussed above, when only one toxicity or half-life value was available, the data point was 

treated as a fixed variable in the model. For chlorophacinone and bromethalin, the single half-life 

values available resulted in steeper distributions, which reflect the potential uncertainty 

associated with a single data point.. 

EPA has used the available toxicity data to construct distributions of possible species sensitivity. 

The variance of each of these distributions is different and owes much to the number and breadth 

of the species randomly selected for testing in addition to the actual inherent variability of 

sensitivity. As discussed in the SAP Background Document, there is uncertainty associated with 

using the standard test species (bobwhite quail and mallard duck) to represent toxicity for 

secondarily exposed bird species. For example, Rattner et al. (2011) reported an LD50 value of 

96.8 mg a.i./kg-bwt for American kestrels (Falco sparverius) consuming diphacinone, which is 

approximately 20 times more sensitive than the LD50 values reported for the bobwhite quail. The 

probabilistic assessment addresses this uncertainty for diphacinone by including the more 

sensitive LD50 value in the estimation of the parameters of the log normal distribution for LD50

values. Results of the assessment indicate that approximately 1% of 100-g predator/scavenger 

birds could receive a dose of diphacinone that would result in risk concerns. However, none of 

the other evaluated rodenticides have data for which an LD50 for raptors or, more generally, 

predatory/scavenging birds is available, so it is uncertain if this increased sensitivity would be 

the same across the different rodenticides or different predatory/scavenging bird species. 

Although this assessment modeled multiple exposure scenarios, including multiple prey types, 

accumulation scenarios, and predator body weights, it does not encompass the entirety of 

possible scenarios. For example, probabilities associated with food intake for the primary and 

secondary consumers were not evaluated in this assessment due to the limited nature of the data 

set. Also, exposure scenarios where contaminated animals were consumed occasionally or 

where target species fed on less than a single day of food for multiple days were not quantified. 

However, if these scenarios were included in the probabilistic model, they would accentuate, 

rather than diminish, the conclusions that chemicals with longer retention times pose greater 

secondary exposure risks relative to chemicals with shorter retention times, and that chemicals 
that can cause LOC exceedances after a single feeding pose greater secondary exposure risks 

relative to those where multiple feeding events on contaminated animals are needed to result in 

LOC exceedances. 

References

Pitt, W. C., Driscoll, L.C., and Sugihara, R.T. 2011. Efficacy of rodenticide baits for the control 

of three invasive rodent species in Hawaii. Arch. Environ. Contam. Toxicol. 60, 533-542.

USEPA. 1993. Wildlife Exposure Factors Handbook. Volume 1. EPA/600/R-93/187a. Office of 

Research and Development, Washington, D.C.
Appendix 1: Distribution Graphs

Graphs in the appendix show the distribution of RQ values derived from the Agency’s limited 

probabilistic risk assessments for each of the six rodenticides considered in the SAP Background 

Document. The RQ value, in log scale, is displayed along the horizontal axis and the likelihood 

of a predator of the particular class experiencing a lethal dose, expressed as percentages by 

increasing value, is displayed along the vertical axis. The vertical red line represents where the 

RQ value is equal to the LOC of 0.5. Portions of distributions that appear to the right of the 

vertical red line indicate species on the distribution with RQ values greater than the LOC, and 

thus at risk for mortality. The percentage of RQ values above the LOC are visually represented 

as the point where the distribution crosses the vertical red line, to the nearest 5%, subtracted from 

100%. These percentages allow for the comparison of risks among chemicals where larger 

percentage values suggest a higher likelihood that a randomly selected bird may achieve a lethal 

dose under the assumptions of this analysis.
100g Birds Dose-Based Exposure

Figure 1. Distribution of Acute RQs for 100g Birds Consuming Mice Exposed to Bait for 1 

Day

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Bromethalin

Chlorophacinone

Diphacinone
Figure 2. Distribution of Acute RQs for 100g Birds Consuming Mice Exposed to Bait for 6

Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000 Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 3. Distribution of Acute RQs for 100g Birds Consuming Mice Exposed to Bait for 14

Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 4. Distribution of Acute RQs for 100g Birds Consuming Rats Exposed to Bait for 1 

Day

Figure 5. Distribution of Acute RQs for 100g Birds Consuming Rats Exposed to Bait for 6

Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 6. Distribution of Acute RQs for 100g Birds Consuming Rats Exposed to Bait for 14

Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
1000g Birds Dose-Based Exposure

Figure 7. Distribution of Acute RQs for 1000g Birds Consuming Mice Exposed to Bait for 1 

Day

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Bromethalin

Chlorophacinone

Diphacinone
Figure 8. Distribution of Acute RQs for 1000g Birds Consuming Mice Exposed to Bait for 6

Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 9. Distribution of Acute RQs for 1000g Birds Consuming Mice Exposed to Bait for 

14 Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 10. Distribution of Acute RQs for 1000g Birds Consuming Rats Exposed to Bait for 

1 Day

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Bromethalin

Chlorophacinone

Diphacinone
Figure 11. Distribution of Acute RQs for 1000g Birds Consuming Rats Exposed to Bait for 

6 Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 12. Distribution of Acute RQs for 1000g Birds Consuming Rats Exposed to Bait for 

14 Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
5000g Birds Dose-Based Exposure

Figure 13. Distribution of Acute RQs for 5000g Birds Consuming Mice Exposed to Bait for 

1 Day

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Bromethalin

Chlorophacinone

Diphacinone
Figure 14. Distribution of Acute RQs for 5000g Birds Consuming Mice Exposed to Bait for 

6 Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone

Figure 15. Distribution of Acute RQs for 5000g Birds Consuming Mice Exposed to Bait for 

14 Days
0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 16. Distribution of Acute RQs for 5000g Birds Consuming Rats Exposed to Bait for 

1 Day

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Bromethalin

Chlorophacinone

Diphacinone
Figure 17. Distribution of Acute RQs for 5000g Birds Consuming Rats Exposed to Bait for 

6 Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 18. Distribution of Acute RQs for 5000g Birds Consuming Rats Exposed to Bait for 

14 Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Dietary-Based Exposure

Figure 19. Distribution of Dietary RQs for Birds Consuming Mice Exposed to Bait for 1 

Day

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00 0.00 0.01 0.10 1.00 10.00 100.00 Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Bromethalin

Chlorophacinone

Diphacinone
Figure 20. Distribution of Dietary RQs for Birds Consuming Mice Exposed to Bait for 6

Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00 0.00 0.01 0.10 1.00 10.00 100.00 Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 21. Distribution of Dietary RQs for Birds Consuming Mice Exposed to Bait for 14

Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.0001 0.001 0.01 0.1 1 10 100

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 22. Distribution of Dietary RQs for Birds Consuming Rats Exposed to Bait for 1 

Day

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00 0.00 0.01 0.10 1.00 10.00 100.00 Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Bromethalin

Chlorophacinone

Diphacinone
Figure 23. Distribution of Dietary RQs for Birds Consuming Rats Exposed to Bait for 6

Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.0001 0.001 0.01 0.1 1 10 100

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone
Figure 24. Distribution of Dietary RQs for Birds Consuming Rats Exposed to Bait for 14

Days

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.0001 0.001 0.01 0.1 1 10 100

Percentile

RQ value (log scale)

Brodifacoum

Difethialone

Warfarin

Chlorophacinone

Diphacinone